Reprinted from the Sept./Oct. 1996, issue of VIPS, the
newsletter of the Visually Impaired Preschool Services of
Louisville, Kentucky.

Optic nerve hypoplasia is a congenital condition in which
the optic nerve has not developed properly; it is too small.
The optic nerve carries visual information from the eye to the
brain. If the optic nerve is underdeveloped, adequate visual
information does not reach the brain for processing. Optical
nerve hypoplasia was once considered a rare condition, but now
it is thought to be the most common congenital defect of the
optic nerve. Depending on the size and abnormality of the
hypoplastic nerve, the vision can range from 20/20 to complete
blindness, or no light perception. Affected eyes also show
visual field defects. In other words, part of the visual
space, such as the upper or lower half of the normal visual
field, may be missing. Color vision is usually normal in an
eye with optic nerve hypoplasia. This is in contrast to optic
nerve injuries that occur later in life. These acquired optic
nerve problems often lead to a loss of color vision.
Optic nerve hypoplasia may affect either one or both
eyes. If both eyes are affected, they may be affected to
different degrees. Children with bilateral optic nerve
hypoplasia usually present in infancy with poor vision and
nystagmus, or shaking of the eyes. In children with one
hypoplastic nerve, the problem is usually manifest by
esotropia, or turning in of the affected eye. Especially if
the one eye is affected, it is very important to see that all
refractive errors are corrected. Optic nerve hypoplasia has
been associated with astigmatism. Amblyopia can further reduce
vision if one eye has better acuity than the other. In other
words, the eye with the poorer vision may be poor in part due
to amblyopia. The "stronger" eye becomes the dominant eye, and
vision does not develop in the weaker eye because of this
dominance. Amblyopia can be treated, and thus a trial of this
type of treatment may be considered.
Optic nerve hypoplasia is often associated with other
brain abnormalities which range from subtle to severe. One
common association is with the pituitary gland. The pituitary
gland secretes many hormones important for growth. Pituitary
dwarfism has been associated with optic nerve hypoplasia. Your
pediatrician will follow your child's growth and development
carefully in order to determine if there is a problem with the
growth hormone or any other hormones. Almost half of all
patients with optic nerve hypoplasia have a problem with the
cerebral hemispheres. Again, this may result in a very subtle
problem, or it may be a severe problem which may further
interfere with vision.
Like most congenital malformations, there is no clear
hereditary pattern to optic nerve hypoplasia, but it is
commonly associated with some conditions such as maternal
diabetes, and also with other eye conditions such as albinism
and aniridia.

Dr. Verderber recently joined the practice of Mahl and
Associates Eye Care Centers, in Louisville. She completed her
residency in Pediatric Ophthalmology at the Children's
National Medical Center in Washington, D.C.